The invention relates to surface mounted piezoelectric vibrators structurally characterized in that a package is constructed of a base having an opening on its upper-surface side and a housing portion formed in its interior, and a cover that seals the opening, and a piezoelectric vibration element and an integrated circuit element are housed in the housing portion of the base (hereinafter, simply referred to as “piezoelectric vibrator”). The invention more particularly relates to improvements in such package constructions of the piezoelectric vibrators.
Very accurate vibratory frequencies can be constantly obtained with the piezoelectric vibrators in which piezoelectric vibration elements, for example, crystal pieces, are used. Such piezoelectric vibrators are, therefore, conventionally employed in diverse fields as reference frequency sources for electronic devices. The piezoelectric vibrators typically have a structure in which an integrated circuit element is housed in a housing portion of a base with insulating properties having an opening on its upper-surface side, a piezoelectric vibration element is securely supported in the upper direction of the integrated circuit element, and a cover is provided to hermetically seal the piezoelectric vibration element. One can simplify the structure of such a piezoelectric vibrator with a relatively small number of components by customizing a one-chip integrated circuit element in which an inverter amplifier, for example, CMOS, is provided as a vibration amplifier, contributing to cost reduction. In recent years, flip-chip bonding is often employed in such piezoelectric vibrators because this bonding technique, in contrast to wire bonding, reduces the piezoelectric vibrators in size and height. An example is disclosed in JP2001-291742A, wherein pads of an integrated circuit element are flip-chip bonded, by means of metallic bumps made of such a material as gold, to internal terminal pads in the housing portion of a ceramic base by supersonic thermocompression bonding.
FIG. 10 illustrates the circuit configuration of a piezoelectric vibrator to be housed in the base.
In the drawing, 100 is an integrated circuit element, and 200 is a piezoelectric vibration element.
The integrated circuit element 100 includes, for example, inverter amplifiers AMP1 and AMP2, a feedback resistor Rf, a limiting resistor Rd, and capacitors C1 and C2. Referring to the other reference symbols, P1 to P3 are signal input and output units of the integrated circuit element 100, and P4 and P5 are signal input and output units of the piezoelectric vibration element 200. An alternating current signal or high frequency signal i1 is outputted from the output unit P3 of the integrated circuit element 100. An alternating current signal i2 flows between the input and output units P5 and P4 of the piezoelectric vibration element 200 and the input and output units P1 and P2 of the integrated circuit element 100. The integrated circuit element and the piezoelectric vibration element are thus connected in the circuit and housed in the base. In the base, the input and output units P1 to P5 for the signals i1 and i2 are connected by means of the pads of the integrated circuit element, internal terminal pads of the base, pads of the piezoelectric vibration element, and wiring patterns.